170 METHODS IN PLANT HISTOLOGY 



pensive rotary washers have no advantage over this method, except 

 that they save your time. 



The prints are then spread out to dry. Let the print drain until the 

 water comes off only in drops; then lay the prints down, face up, on 

 blotting paper or newspaper and wipe off surplus water with a large 

 tuft of cotton. When almost dry — not quite "bone dry" — they can be 

 piled up, one on top of another, or with a thin piece of white blotting 

 paper between, and put under gentle pressure. A board with two or 

 three bricks will be enough. If put under pressure too soon, prints are 

 likely to wrinkle. 



If glossy paper is used, place the prints face down upon a clean 

 squeegee plate, and press them with a rubber roller or with a rubber 

 like a window cleaner. When dry, they should come off easily. 



OVEREXPOSURES AND UNDEREXPOSURES 



Negatives, lantern slides, and paper prints which have been over- 

 exposed or underexposed can often be reduced or strengthened until 

 they are as good as if the exposures had been correct. 



Reducing overexposures. — The reducing solution should be applied 

 as soon as the negative, lantern slide, or paper print comes from the 

 fixing bath. If they have been washed and dried, they should be 

 soaked in water for five or ten minutes before using the reducing solu- 

 tion. 



The following is a good reducing solution for most purposes : 



Metric Apothecaries' 



/ Water 473 c.c. (16 oz.) 



\ Hyposulphite of soda 31 g. (1 oz.) 



f Water 473 c.c. (16 oz.) 



\ Red prussiate of potassium 31 g. (1 oz.) 



Solution B must be protected from the light. Cover the bottle with 

 black paper and keep it in the dark when not in use. 



Mix only for immediate use 8 parts of A to 1 of B and use in rather 

 subdued light. A darkroom is not necessary, but avoid bright light. 



When the negative or lantern slide becomes satisfactory, wash it in 

 water as thoroughly as if it had just come from the ordinary hypo 

 fixing solution. 



The reduction can be done locally with a tuft of cotton. 



When possible, it is better to make a new, correct exposure than to 

 reduce or intensify an incorrect one. 



